The above prior application discloses an apparatus and method for oiling fast moving metal strips in rolling mills or the like. It is required that the strip be oiled uniformly across its entire width with the minimum possible consumption of oil and without polluting the surrounding environment. In the prior application, as in the present invention, oil is attracted to the moving strip, which is grounded, by electrostatic attraction. Under the effect of such attraction, small discrete streams of oil are pulled through outlet openings of an adjacent oil header and impinge on the opposing face of the moving strip to coat the same, with or without the assistance of external pressurized air sprays which disperse the small streams of oil into a number of fine overlapping oil sprays across the width of the strip.
A problem can arise with the arrangement disclosed in the prior application, and it is the main objective of this invention to eliminate this problem or drawback entirely even before it can arise. The problem in question arises when the header, which delivers oil by electrostatic attraction onto the moving metal strip, is not level and the oil within the header, for this reason or for other reasons, is not evenly distributed in the header along its full length. Even if the header is perfectly level, which condition is difficult to achieve and maintain, the oil within it still may not be evenly distributed due to inherent surging action in the pump system supplying the header with oil. Furthermore, there will always tend to be more oil in the header at the point or points where the oil enters the header under the influence of the pumping means. Even when plural pumps are used to deliver oil to several different inlets along the length of the header, completely even oil distribution is never attained. As a result of this unevenness of oil distribution in the header, some areas of the metal strip undergoing oiling will receive too much oil and other areas too little, with the final result that the strip will not be evenly oiled across its full width as desired. Also, the lack of even distribution of oil within the header will ultimately result in excessive consumption of oil by the oiling system.
As stated, the object of this invention is to deal with this prior art problem of oil distribution within the oiling header to enable even or uniform delivery of oil onto the strip across its full width with minimum oil consumption.
In achieving this main objective, a perforated oil diffuser plate is placed in the header dividing it into two chambers. A single pumping source delivers oil from a reservoir to one chamber of the header on one side of the diffuser plate, and the oil passes through the diffuser plate in order to enter and fill the other chamber of the header, and in so doing even distribution of oil within the second chamber of the header throughout its entire length is achieved and is easily maintained during continued operation of the system. Consequently, the strip being oiled which receives its oil by electrostatic attraction from the second chamber of the header in which the oil is evenly distributed is coated with oil uniformly across its entire width and a minimum volume of oil is consumed in the process.
Simultaneously, the perforated diffuser plate forms the charging electrode for the bath of oil filling the two chambers of the header in which the diffuser plate is submerged. Thirdly, the diffuser plate, by virtue of its relatively small aperture sizes, serves as a final filter for the oil passing through the header prior to delivery onto the metal strip.
In accordance with the invention, excess oil from the strip falls back into a recovery tank below the header and is efficiently returned from this tank back to the oil reservoir where it can be reused in the oiling system.
Consumption of oil, compared to the known prior art, is reduced by the invention by as much as fifty percent. The oil will be uniformly applied to the metal strip regardless of variations in strip speed. The entire strip oiling apparatus can be placed in a floor space of only about 1.5 feet lengthwise of the strip.
An important benefit and feature of the invention resides in the ability of the system to be turned off and on merely by throwing a switch in the electrostatic charging system. For example, when such switch is in one position, the moving metal strip may be grounded and will attract oil onto its surface facing the oiling header across its entire width. If the switch is in the other position, the ground circuit through the strip may be broken and consequently no oil will be attracted to the strip and the system is shut off entirely.
Furthermore, the system inherently possesses the capability of adjusting automatically to the width of the metal strip, whether wide or narrow, whenever the electrostatic system is on or energized. For example, if the strip being oiled extends substantially for the full length of the header, oil will be attracted from the header along its full length. If the strip happens to be very narrow, equalling only a small fraction of the header length, then the oil will be attracted only from that small region of the header across which the strip is moving. If the system is turned on electrically, whenever a strip of any width up to the maximum width which can be handled, the header will deliver oil by electrostatic attraction uniformly across the full width of the strip, and if no strip is present, no oil will leave the header as there will be nothing to attract the oil. Should there be areas on a moving strip which it is desired to coat with oil and other areas which are to remain uncoated, then the system can be rendered active or inactive, as desired, merely by the throwing of an on-off switch.
Other features and advantages of the invention will become apparent during the course of the following description.